Embodiments of the invention generally relate to an article having a protective coating for use in a semiconductor processing chamber and a method of making the same.
Integrated circuits have evolved into complex devices that can include millions of transistors, capacitors and resistors on a single chip. The evolution of chip designs continually requires faster circuitry and greater circuit density that demand increasingly precise fabrication techniques and processes. One fabrication process frequently used is chemical vapor deposition (CVD).
Chemical vapor deposition is generally employed to deposit a thin film on a substrate or a semiconductor wafer. Chemical vapor deposition is generally accomplished by introducing a precursor gas into a vacuum chamber. The precursor gas is typically directed through a showerhead situated near the top of the chamber. The precursor gas reacts to form a layer of material on the surface of the substrate that is positioned on a heated substrate support typically fabricated from aluminum. Purge gas is routed through holes in the support to the edge of the substrate to prevent deposition at the substrate""s edge that may cause the substrate to adhere to the support. Deposition by-products produced during the reaction are pumped from the chamber through an exhaust system. One material frequently formed on substrates using a chemical vapor deposition process is tungsten. A precursor gas that may be used to form tungsten generally includes tungsten hexafluoride (WF6) and silane. As the silane and tungsten hexafluoride mix, some xe2x80x9cstrayxe2x80x9d tungsten (i.e., tungsten that does not deposit on the substrate) deposits on the showerhead and other chamber components. The stray tungsten film builds on the showerhead and may become a source of contamination in the chamber. Eventually, the stray tungsten may clog the holes in the showerhead that facilitate passage of the precursor gas therethrough and necessitating the showerhead be removed and cleaned or replaced.
To extend the interval of time between routine maintenance of the showerhead, fluorine-based chemistries are generally used to clean (i.e., etch away) the stray tungsten film. However, the use of fluorine, while advantageous for removing tungsten, reacts to form a layer of aluminum fluoride on the heated support and other surfaces that are made of aluminum, a material commonly used in CVD chambers. The aluminum fluoride layer formed in this manner has a generally rough surface topography. The rough surface of an aluminum fluoride layer on the heated aluminum support creates a leak path that impairs the vacuum used to chuck or hold the substrate to the heated support. Additionally, the aluminum fluoride layer often cracks and peels over the course of thermal cycling of the heated support, and thus becomes a source of particulate contamination.
One solution to the formation of aluminum fluoride on heated aluminum supports is to fabricate the heater from ceramic materials that are resistant to fluorine. However, ceramic supports are difficult to fabricate and, consequently, are very costly as compared to conventional aluminum heaters used in CVD processes.
Another way to prevent fluorine reaction with the aluminum support is to deposit an aluminum fluoride barrier layer on the support. However, conventional methods of applying aluminum fluoride to the support result in aluminum fluoride barrier layers having about 20 to about 30 percent of the grain structure in the beta phase and about 70 to about 80 percent of the grain structure in the alpha phase. Aluminum fluoride layers having greater than about 10 percent of the grain structure in the beta phase do not adhere well to aluminum and are also prone to cracking. As the aluminum fluoride barrier layer cracks, fluorine, reacting with the underlying aluminum, causes additional growth of aluminum fluoride under the layer, eventually causing the barrier layer of aluminum fluoride to separate from the support. Flakes of aluminum fluoride from the peeled barrier layer are a source of particulate contamination which is detrimental to process yields. Other aluminum surfaces within the processing chamber have similar problems.
Therefore, there is a need for coating that protects aluminum surfaces in semiconductor processing chambers.
An article having a protective coating for use in semiconductor applications and method for making the same is provided. In one aspect, an article for use in a semiconductor processing chamber includes a coating comprising an aluminum fluoride or a magnesium fluoride layer applied in a semi-liquid, semi-solid state to the aluminum surface of a chamber component.
In another aspect, a substrate support is provided having a protective coating. In one embodiment, the substrate support includes a support body having a heating element disposed therein. A coating comprising an aluminum fluoride or magnesium fluoride layer is applied to an aluminum surface of the support body in a semi-liquid, semi-solid state.
In another aspect, a method of coating an aluminum surface of an article utilized in a semiconductor deposition chamber is provided. In one embodiment, a method of coating an aluminum surface of an article utilized in a semiconductor deposition chamber includes the steps of heating a coating material to a semi-liquid, semi-solid state, the coating material comprising at least one material from the group consisting of aluminum fluoride and magnesium fluoride and depositing the heated coating material on the aluminum surface. The protective coating has a beta phase grain orientation of less than about 10 percent that provides good adhesion to aluminum and resists cracking, flaking and peeling. Some articles that may be advantageously coated using this method include showerheads, blocker plates, support assemblies and vacuum chamber bodies among others.
In another aspect, a method of coating an aluminum surface on a substrate support includes the steps of forming a plasma from an inert gas, heating aluminum fluoride with the plasma, and spraying the heated aluminum fluoride on the aluminum surface.